How to represent variable JSON data with Proto definition

[Ayush Shah]

Newbie question... If I have the following sample "User" JSON data:

{

  firstName: 'Bob'

  lastName: 'Smith',

  email: 'b...@gmail.com',

  metadata: {

    // a plain JS object that 

    // - will always exist and be at least an empty {} object

    // - could potentially contain any number of properties and values, depending on specific "user"

  }

}

How do I represent the metadata property within proto definition? I've tried

message User {

  message Metadata {}

  string email = 1;

  string firstName = 2;

  string lastName = 3;

  Metadata metadata = 4;

}

or using `Any`

message User {

  string email = 1;

  string firstName = 2;

  string lastName = 3;

  google.protobuf.Any details = 4;

}

but without success. Working within Node.js if relevant. Any help is much appreciated. Thanks!

[Em Rauch]

I think what you're looking for is `google.protobuf.Struct details`; Struct is the type which allows any JS object to parse into it and acts like a `map<string, SomeJSONValueType>` (including recursively a struct inside if its another JS object in there).

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[Austin Bennett]

Might not work for all you need, but could try:  https://protobuf.dev/reference/protobuf/google.protobuf/#struct

In prior use cases, we've also treated things like your metadata field as a string, and then parsed the string field to extract anything relevant. 

In general, I prefer to have the proto define anything in it that might be optional, rather than [ "could be anything" ].  That allows for some nicer handling, BUT means you also would want to be in sync with the data creator/producer, which isn't always possible.  

Good luck!  

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[Ayush Shah]

Thanks for the response, I tried using Struct to send requests and responses but on the server side I am only receiving  the empty response every time.I checked online many people faced same issue so is it bug or implementation problem.

Any help is much appreciated. Thanks!

[Em Rauch]

It would be extremely surprising if Struct simply did not work for generically parsing JSON; it's in very wide usage both within and outside of Google.

Do you have a reproduction or references to the other people facing issues with it?